Known in the art are polymer-based compositions, employed for improvement of adsorption of hydrocarbons and separation of hydrogen isotopes.
U.S. Pat. No. 2,722,504 teaches a composition consisting of a metal oxide (Al.sub.2 O.sub.3, MoO.sub.3, CuO, V.sub.2 O.sub.5 and the like), an oxide or sulphide of a transition metal with an atomic weight of from 22 to 42 and silicone adapted for improvement of a selective adsorption of hydrocarbons compared to oxide materials untreated with silicone.
U.S. Pat. No. 3,981,976 teaches a composite catalyst for separation of hydrogen isotopes compared of a mixture of oxide of metals such as AlO.sub.2 O.sub.3, WO.sub.3, MgO, SiO.sub.2 and the like, or of graphite with oxides of metals, of Group VIII of the periodic system and a polymer possessing hydrophobic properties.
There prior art compositions, however, cannot serve as membrane catalyst selectively permeable to hydrogen.
At the present time as hydrogen-permeable membrane catalysts use is made of palladium-based alloys manufactured as a foil, for example an alloy containing 85% by mass of Pd and 15% by mass of Pt (cf. Japanese Pat. No. 11362) or as a tube (U.S. Pat. No. 3,201,620). For the manufacture of such membranes a considerable consumption of palladium per 1 cm.sup.2 of the catalyst surface area is required. Thus, for the manufacture of a catalyst as taught in Japanese Pat. No. 11362, it is required to use 0.24 g of palladium per 1 cm.sup.2 of the catalyst surface; according to U.S. Pat. No. 3,201,162 0.20 g of Pd per 1 cm.sup.2 of the catalyst surface area is required.
Also known in the art is a method for producing a hydrogen-permeable membrane catalyst by rolling as a foil with a thickness of from 0.05 to 0.1 mm of palladium or alloys thereof (cf. Doklady Akademii Nauk SSSR, 211, No. 3, 624, 1973).
With the view to save noble metals, there has been suggested a method for the manufacture of a membrane catalyst by sublimation of an alloy based on palladium onto a polymeric film selectively permeable for hydrogen; this film is applied onto a reinforcing substrate made of a sintered powder metal material and hindered no penetration of the reagents (cf. USSR Inventor's Certificate No. 593351 of Oct. 21, 1977; U.S. Pat. No. 4,132,668; Jan. 2, 1979).
This method makes it possible to produce a membrane catalyst in the form of a three-layered composition consisting of a sintered powder metal substrate based, for example, on copper, nickel, stainless steel, a polyorganosiloxane polymer film and a thin layer of a catalytically active palladium-based component.
In this catalyst the catalytically active component is used insufficiently due to a non-uniform thickness of the layer of palladium over a large area of the catalyst.
Furthermore, the size of this composite catalyst is limited thus causing limitation of a unit capacity of the catalytic hydrogenation plant. The limited size of this catalyst is due to small size of the vacuum chambers employed for sublimation of palladium. The composite membrane catalyst contains palladium or an alloy thereof in a low-disperse form, wherefor for the manufacture of a unit area of the catalyst surface a rather great amount of palladium is consumed.